In the field of communication systems, including wireless and/or cellular communication systems, various techniques are known for concurrently utilizing a physical channel for both transmitting and receiving operations, i.e. for communication in both transmitting and receiving directions from the viewpoint of a system entity in questions. One of these known channel utilization techniques is Time Division Duplex (TDD) in which transmitting and receiving operations utilize a common frequency spectrum while being temporally separated from each other.
The TDD technique is effective by offering flexible deployments without requiring a pair of spectrum resources, which is especially beneficial in wireless communication systems having limited spectrum resources. Further, the TDD technique is effective by allowing asymmetric uplink-downlink (UL-DL) resource allocations in that a different number of resources (e.g. blocks, frames, subframes or the like) are allocated for uplink and downlink communications. In view of these features, TDD is currently utilized in various communication systems, including wireless and/or cellular communication systems, e.g. LTE and LTE-A systems.
In current LTE/LTE-A deployments, the same TDD (UL-DL) configuration in each cell is assumed, since otherwise interference between UL and DL, including both base station-to-base station (e.g. eNB-to-eNB) interference and terminal-to-terminal (e.g. UE-to-UE) interference, arises and needs to be considered especially in neighboring cells. However, adopting the same UL-DL configuration in each cell is typically inadequate in cellular communication systems. This is because different traffic situations in different (including neighboring) cells could most appropriately be handled by different UL-DL configurations, i.e. a differently distributed allocation of the available resources to UL and DL communications. For example, in local area (LA) networks, due to a small number of active UEs per cell, the traffic situation may fluctuate frequently, and flexible TDD re-/configuration to adapt to the traffic (i.e. traffic adaptation) could be expected to provide improved resource efficiency and provide power saving. Namely, since in LA networks the typical cell size is small in comparison with a typical (macro) cell and the number of terminals connected to each base station in the network is not large, there is an increased possibility that the traffic situation in different LA cells may only be adequately handled by different UL-DL configurations.
Accordingly, in case TDD configurations are set adaptively in different cells e.g. corresponding to the traffic (fluctuation) status therein, a new type of interference between such cells could be introduced as compared with the scenarios without such flexible TDD configuration, i.e. DL-UL interference and UL-DL interference, generally referred to as inter-cell cross-link interference herein. For example, when neighboring cells perform traffic adaptation by selecting UL-DL configurations in which at least one (flexible) subframe is assigned for different link directions, such inter-cell cross-link interference could occur for this at least one subframe.
The above considerations generally hold for all kinds of cellular communication systems, but may be particularly relevant in layered heterogeneous network (HetNet) deployments in which macro (high power) and micro, pico or femto (low power) cells are deployed in different logical layers in parallel. Accordingly, such inter-cell cross-link interference could equally occur between macro cells and between a macro cell and a micro, pico or femto cell.
As one measure for inter-cell interference mitigation in the context of enhancements to interference management and traffic adaptation (eIMTA) for LTE TDD, a cell clustering interference mitigation (CCIM) scheme has been proposed.
In the CCIM scheme, cell clusters are formed, wherein each cell cluster can comprise one or more cells, typically micro, pico or femto cells in a layered heterogeneous network deployment. The active transmissions of all cells in each cell cluster shall be either uplink or downlink in any subframe or a subset of all subframes, so that eNB-to-eNB interference and UE-to-UE interference can be mitigated within the cell cluster. Hence, in order to enable a TDD subframe re-/configuration satisfying the above requirement on active transmissions of all cells in the same cluster, coordination between the multiple cells belonging to the same cell cluster is needed.
However, no measures are currently known or specified for realizing such needed coordination between the multiple cells belonging to the same cell cluster for enable a TDD subframe re-/configuration satisfying the above requirement on active transmissions of all cells in the same cluster. Stated in other words, no measures are currently known or specified, which would be applicable to enable a re-/configuration of flexible TDD communication within a cell cluster so as to facilitate inter-cell interference mitigation, especially cell clustering interference mitigation, in cellular communication systems such as e.g. in layered heterogeneous network deployments.
Thus, there is a need to provide measures to enable cell clustering based configuration of flexible TDD communication, such as e.g. in layered heterogeneous network deployments